The present invention relates to inspection systems of a semiconductor product and methods thereof, and especially to systems and methods for measuring distances between semiconductor patterns.
Conventionally, a semiconductor wafer (hereinafter, referred to as ‘wafer’) includes a plurality of integrated circuit devices that are repeatedly disposed. The integrated circuit devices are fabricated by applying a plurality of semiconductor fabrication processes to a wafer. After performing a predetermined semiconductor fabrication processes, various kinds of inspection steps may be applied to determine whether the performed semiconductor fabrication processes are carried out properly. According to the kinds of the performed semiconductor fabrication processes, the inspection may be performed in the various kinds of methods. For example, a step for measuring a thickness of a material layer may be carried out after depositing the material layer. A step for measuring widths, lengths or distances of patterns may be performed after a photolithographic process or an etch process to form patterns.
Recently, as a high integration of semiconductor devices is rapidly progressing, a distance (i.e., a width, a length, or a space) between micro patterns becomes important. Therefore, micro patterns of tens of nanometers to several micrometers should be carefully measured and managed, even though carelessness is often associated with measurements and management of macro patterns of several micrometers to hundreds micrometers.
Conventionally, the distance between the macro patterns is measured by equipment such as an optical microscope. A method for measuring a distance between macro patterns using conventional methods will be explained referring to FIG. 1.
FIG. 1 is a schematic view illustrating a conventional method for measuring a distance between two spots on a wafer.
Referring to FIG. 1, an optical microscope has a predetermined field of view (hereinafter referred to as ‘view-field’). A picture of the view-field is changed according to a magnification of the optical microscope. For example, an area of the wafer 1 shown in a low-magnification view-field 5 is larger than that shown in high-magnification view-fields h1, h2, h3 and h4. Conversely, the high-magnification view-field h1, h2, h3 and h4 display more detailed pictures compared to the low-magnification view-field 5.
The conventional equipment having the optical microscope includes a scaled ruler 4 displayed in the view-field.
A method for measuring a distance between the macro patterns using the conventional equipment having the optical microscope will be explained hereinafter. First, a magnification of the optical microscope is lowered to secure a low-magnification view-field 5 showing both of first and second spots 2 and 3 to be measured. Then an operator sets the ruler 4 in the low-magnification view-field 5 to the spots 2 and 3 and reads the scale of the ruler 4, so that the distance between the spots 2 and 3 is measured.
In the above method, the low-magnification view-field 5 may have a real distance error of the measured macro pattern because of the low accuracy of the low-magnification view-field 5. As the magnification of the optical microscope becomes lowered from high to low, a real distance defined by the unit scale of the ruler 4 may be increased. Therefore, even if a small error occurs in the process for setting the scales of the ruler 4 to the spots 2 and 3 depending on the operator's eye view, it may become a large error in the distance between the macro patterns.
To measure a macro pattern distance using high magnification, at least one stepping point between the first and second spots 2 and 3 is selected. In this case, the selection of the stepping point depends on the eye of the operator. FIG. 1 illustrates the first, second and third stepping points a1, a2 and a3. A first high magnification view-field h1 is secured by increasing a magnification of the optical microscope. The first high magnification view-field h1 displays the first spot 2 and the first stepping point a1 at the same time. A first distance L1 between the first spot 2 and the first stepping point a1 is determined using the scales of the ruler 4 in the first high magnification view-field h1 by the operator, etc. The first high magnification view-field h1 is then moved to a second high magnification view-field h2 displaying the first and second stepping points a1 and a2. A second distance L2 between the first and second stepping points a1 and a2 is measured using the ruler 4 in the second high magnification view-field h2. Then, as illustrated in FIG. 1, the second high magnification view-field h2 is moved to third and fourth magnification view-fields h3 and h4 serially. Simultaneously, a third distance L3 between the second and third stepping spots a2 and a3, and a fourth distance L4 between the third stepping spot a3 and a second spot 3 are measured serially. The first, second, third, and fourth distances L1, L2, L3, and L4 are summed to calculate the distance between the first and second spots 2 and 3.
The above method for measuring a distance using the high magnification view-fields h1, h2, h3, and h4 may decrease a measuring error compared to that using the low magnification view-field 5. However, various errors can occur in the method using high magnification view-fields h1, h2, h3, and h4. That is, the selection of the stepping points a1, a2 and a3 depends on the eye of the operator, so that the error with respect to the position of the stepping points a1, a2, and a3 can occur according to the movement of the view-fields. In addition, the distance between the first spot 2 and the second spot 3 is measured several times partially. Thus, errors in measurement may occur repeatedly and accrue towards a larger total error. That is, small errors in measurement may occur repeatedly compared to the method using the low magnification view-field 5. As a result, the error of the measured distance of the macro patterns may be degraded in the method using the high magnification. In addition, the method using the high magnification may be complicated due to the process of selecting the stepping points a1, a2, and a3, with the increasing partial measurements for measuring the total distance.